This invention relates to light exposure apparatus suitable for use in light exposure for the pattern formation in the manufacture of color picture tubes and semiconductor integrated circuits.
In the formation of a pattern of phosphors of varying colors on the inner surface of a face panel in a color picture tube, for example, rays of light are radiated from the light source so as to advance in the same paths as would be followed by electron beams and then impinge upon a photosensitive film covering the inner surface and consequently light-expose the points of impingement. In this case, the amount of light exposure is proportional to the intensity of light impinging upon the photosensitive film, and this operation of light exposure has entailed the problem that, for a certain length of time after the light source has been turned on, the intensity of light is varied to impair the uniformity of the amount of light exposure and that of pattern formation.
A search for the cause of this phenomenon has revealed that some of the filters and lenses used in the optical system of the light exposure apparatus suffer variation of their cut-off frequencies on the short wavelength side as the temperature varies and that when these filters and lenses gradually gain in temperature with elapse of time after the light source has been turned on, the intensity of the light impinging upon the surface exposed to the light is varied proportionally to the rise of the temperature.